1. Field of the Invention
The invention relates to a simple and inexpensive acylation process, especially for the acetylation of aminocarboxylic acids. Particularly expensive amino acids such as phenylalanine and tryptophan can thus be advantageously acylated.
It is known to acylate aminocarboxylic acids with the aid of carboxylic acid anhydrides or halides. The known methods result neither in high yields nor in products of high purity. Particularly, the acetylation of phenylalanine with acetic anhydride yields an impure product. The more one strives for an N-acetylphenylalanine of satisfactory purity, the greater is the excess of acetic anhydride that must be used. The acetic acid that is produced in acetylation with acetic anhydride interferes with the isolation of the product and prevents high yields of pure product.
Good yields and purities result from the acetylation of aminocarboxylic acids with ketene in accordance with German Offenlegungsschrift No. 2,741,081. However, ketene always has to be produced freshly in a generator and must be used immediately. This method, therefore, is profitable only with regard to relatively large quantities.